(a) Field of the Invention
The invention relates to a method and apparatus for the automatic control of the air/fuel ratio of a catalyst IC engine using a controller and a lambda probe, which is arranged in the exhaust pipe of the IC engine, the lambda controller also responding to the signals of at least one exhaust gas temperature probe and processing the same to adjust the set point.
(b) Description of Prior Art
The German pre-examination specification No. 3,410,930 describes a device of this type, in which the fuel supply rate to a mixer is controlled by means of a lambda controller dependent on the signals of a lambda probe. The lambda probe produces a signal which is a function of the actual air/fuel ratio (in what follows referred to as the lambda value), for instance by detecting the difference between the O.sub.2 partial pressure of the engine exhaust gas and of the ambient air and producing a corresponding electrical output signal. It is known that the characteristic curve of such probes is dependent on the temperature of the exhaust gas to which the probe is exposed. This effect is taken into account in the known device inasmuch as the controller responds to the signals of a temperature sensor arranged in the exhaust gas pipe and processes the signals to effect a temperature compensation of the lambda control function. However it has become clear that the overall system is subject to other effects. If for instance the properties of the lambda probe or the catalyst change owing to age, the set point of the lambda controller will have to be adjusted to achieve operation with optimum contaminant data.